The present invention relates to a hose with corrugated metal tube, which is suitable for fuel conveying hose for automobiles, refrigerant conveying hose or any other fluid conveying hose, and more particularly to fastening structure assembled on an end portion thereof.
Typical rubber hoses, for example, made of blended product of acrylonitrile-butadiene rubber and polyvinyl chloride (NBR/PVC blend) which is excellent in resistance to gasoline permeability, have been used for conveying fuel for automobiles or the like in view of their high vibration-absorbability, easy assembling or the like. However, for the purpose of global environment protection, the regulations have been recently tighten against permeation of fuel for automobiles or the like, and are anticipated to be further tighten in the future. Further, hoses are demanded to meet the requirements to convey highly permeable fluid such as hydrogen gas used in fuel cells or carbon dioxide (CO2) refrigerant.
Then it is anticipated difficult to satisfy the future requirements with hoses made only of organic materials such as rubber or resin.
Accordingly, it is currently considered to adapt a hose with a corrugated metal tube as an inner layer because the hose with a corrugated metal tube is expected to have an extremely high fluid impermeability to meet the demand for a fluid impermeable hose.
As for hose with corrugated metal tube, such hoses as disclosed in the following Document 1, Document 2 and Document 3 are known.
Document 1 JP, A, 2001-182872
Document 2 US20020007860A1
Document 3 JP, U, 51-150511
In case of the hose with corrugated metal tube, even if adapted for hydrogen gas of small molecular mass used for fuel cells, a corrugated metal tube in or as an inner layer reduces gas permeation zero, i.e., completely eliminates perm ation of gas.
However, as an inner layer, i.e., a corrugated metal tube in the hose with corrugated metal tube is difficult to deform, if the hose with corrugated metal tube is adapted, it will be a problem how to construct fastening structure on an end portion of the hose with corrugated metal tube so as to assure sealing property thereon.
Up to now, as shown in FIG. 11, fastening structure for typical rubber hose is usually constructed as in following manner. First, a rigid metal inert pipe or connecting part 200 is inserted in a hose body 202, a socket fitting 204 including an inwardly directed collar-like base portion 206 is fitted onto the hose body 202. And then, the socket fitting 204 or a sleeve thereof is securely compressed or swaged radially inwardly to the hose body 202. The hose body 202, the insert pipe 200 and the socket fitting 204 are securely fastened in unitary relation with one another by securely compressing or swaging the socket fitting 204 or the sleeve thereof radially inwardly to the hose body 202 and a seal is thereby provided between an inner surface of the hose body 202 and the insert pipe 200.
And, fastening structure as shown in FIG. 12 is basically same as the one as shown in FIG. 11. In this fastening structure, a hose body 208 has multi-layers, an inner rubber layer (inner elastic layer) 210, a reinforced layer 212 and an outer rubber layer (outer elastic layer) 214. A metal insert pipe or pipe-shaped connecting part 216 is inserted in the hose body 208, and a socket fitting 218 is fitted onto the hose body 208. A socket fitting 218 includes a sleeve 220 and an inwardly directed collar-like base portion 222. The socket fitting 218 is securely compressed or swaged radially inwardly. Thereby the hose body 208 is, along with the socket fitting 218, fixedly secured to the connecting part 216. A reference S in FIG. 12 indicates a gap defined in a tip-end side of the hose body 208.
Though an end portion of the hose body 208 is fixedly secured to the connecting part 216 by securely compressing or swaging the socket fitting 218, the outer rubber layer 214 may be cut away on a portion on which the socket fitting 218 is fitted so as to expose the reinforced layer 212 partly, the socket fitting 218 may be fitted onto the reinforced layer 212 exposed, and the socket fitting 218 may be securely compressed or swaged radially inwardly to the reinforced layer 212.
The reason is that if the outer rubber layer 214 remains uncut while socket fitting 218 is fitted onto an outer side thereof and the socket fitting 218 is securely compressed and swaged radially inwardly, a fastening force applied by the socket fitting 218 may be not exerted sufficiently to an end portion of the hose body 208 due to elasticity of the outer rubber layer 214 and pull-out resistance of the hose body 208 is decreased.
In such fastening structure or sealing structure assembled on an end portion of the typical conventional hoses as shown in FIGS. 11 and 12, an end portion of the hose body 202, 208 may be favorably sealed just by securely compressing or swaging the socket fitting 204, 218, as an inner surface of the inner rubber layer 210 (in FIG. 12) can sufficiently closely contacts with an outer surface of the insert pipe or connecting part 200, 216 thanks to elasticity thereof.
However, in case of a hose with corrugated metal tube in or as an inner layer, close-contact relation is hardly obtained between the corrugated metal tube and the insert pipe or the connecting part. If there is a scratch on a surface of the corrugated metal tube in a compressed or swaged range, internal fluid easily leaks out of that scratch.
Therefore, in such a hose with corrugated metal tube, a tip end of the corrugated metal tube is bonded to the insert pipe or connecting part by welding to assure sealing property therebetween.
However, a great deal of difficulties is presented in welding operation for sealing an end portion of the hose. It not only raises production cost of a hose, but also lowers mechanical strength of an insert pipe or a corrugated metal tube due to affection by heat and thereby will be a factor to damage quality assurance of a hose.
Some problems are explained as above, specifically with an example of a hose conveying hydrogen gas used in fuel cells. However, these problems will arise in common in case that a hose with corrugated metal tube is adapted for conveying refrigerant of small molecular mass such as CO2 which is high in gas permeability or other fluid, or a hose with corrugated metal tube is adapted in fields under severe regulations against gas permeation, for example, for conveying automobile fuel or the like.
Accordingly, it is an object of the present invention to provide fastening structure assembled on an end of a hose with corrugated metal tube having sufficient sealing property or sufficient sealing property and mechanical strength.